come fertilized unless different prothalli of the proper kinds 

 are sufficiently near to enable the antherozoides to pass from one 

 prothallium to another. 



Lowe has shown the necessity for this, quite clearly, although 

 he has apparently demonstrated the possibility of antherozoides 

 being carried from one prothallium to another by insects. But 

 all this will serve to show you how unlikely it is for the hybridi- 

 zation of ferns to occur very often in nature, That, however, it 

 may sometimes — however rarely — be, and has been brought about 

 in certain instances, we have some fairly good presumptive evi- 

 dence, if not positive proof. I do not see how we can ever obtain 

 absolute proof of hybridity in nature, because it is manifestedly 

 impossible for us to observe the process through which it is 

 brought about ; nor do I see how we can obtain positive proof 

 through mixed spore sowing, as it is equally impossible for us to 

 determine from which species the germinating spores came. It 

 seems to me that in all such cases there will always be an element 

 of uncertainty that will compel us to rely altogether upon induc- 

 tive reasoning for our conclusions which are not always likely to 

 be safe. 



There is, however, a way — suggested by Lowe's experiments 

 in dividing prothalli — by which proof of hybridity may be ob- 

 tained, if one has the necessary skill and patience to undertake 

 it, — and that is by first sowing the spores from different species 

 separately, and then afterward dividing the resultant prothalli so 

 as to bring the antheridium portion of a prothallium of one 

 species, and the archegonium part of a prothallium of another 

 species togther, until they coalesce and fertilization takes place. 

 If this method should succeed the resulting fern plant must 

 necessarily be a hybrid. 



I do not find any evidence of this having been tried in the 

 way here suggested, but Lowe has recorded some successful ex- 

 periment in dividing prothalli and raising fern plants by bring- 

 ing portions of different prothalli together, and Prof. Bowen has 

 recently given an account, in the Annals of Botany for December 

 1897, of Poly podium Sckneideri, which he considers to be a good 

 hybrid between Polypodiuin aureum and a form of Polypodium 

 vulgare, called var. elegantissimum, and which was raised by 

 first sowing spores of each species separately, and then putting 

 the resultant prothalli together afterward, a method, however, 

 which does not eliminate every possible chance for doubt as 



